diff --git a/tox.ini b/tox.ini
index 06a9d59..79354a3 100644
--- a/tox.ini
+++ b/tox.ini
@@ -20,11 +20,13 @@ commands =
     stestr slowest
 
 [testenv:pep8]
+basepython = python3
 sitepackages = False
 commands =
   flake8 {posargs}
 
 [testenv:cover]
+basepython = python3
 setenv =
     VIRTUAL_ENV={envdir}
     PYTHON=coverage run --source subunit2sql --parallel-mode
@@ -34,9 +36,11 @@ commands =
   coverage html -d cover
 
 [testenv:venv]
+basepython = python3
 commands = {posargs}
 
 [testenv:docs]
+basepython = python3
 commands = python setup.py build_sphinx
 
 
@@ -50,10 +54,12 @@ ignore = E125,E123,E129,H305,E711
 exclude = .venv,.git,.tox,dist,doc,*egg,build,releasenotes
 
 [testenv:generate_samples]
+basepython = python3
 commands =
     oslo-config-generator --config-file config-generator/subunit2sql.conf
     oslo-config-generator --config-file config-generator/sql2subunit.conf
     oslo-config-generator --config-file config-generator/subunit2sql-db-manage.conf
 
 [testenv:releasenotes]
+basepython = python3
 commands = sphinx-build -a -E -d releasenotes/build/doctrees -b html releasenotes/source releasenotes/build/html